In recent years, current measurement devices have been used for non-contact measurement of alternating current flowing in electric lines of a distribution board and/or the like, in order to measure the consumed power of a plant, a household and/or the like.
A current measurement device of this type is disclosed in, for example, Patent Literature 1. The current measurement device of Patent Literature 1 comprises a conductor for generating a magnetic field in the surroundings through conducted alternating current, and two detection coils for outputting an inductive voltage signal in accordance with the magnetic field.
One of the two detection coils is disposed on a surface of the conductor via an insulating sheet. The other detection coil is disposed separately from the conductor so as not to receive the influence of the magnetic field generated from the conductor. In the one detection coil, an inductive voltage signal is generated in accordance with the change in the magnetic field that is the sum of the magnetic field generated from the conductor and an external magnetic field that is magnetic noise. In the other detection coil, an inductive voltage signal is generated in accordance with only the external magnetic field. The two detection coils are connected to each other in series and in opposite polarity. That is to say, the two detection coils are connected so that the changes in the inductive voltage signals generated by the external magnetic field are opposite. Consequently, the external magnetic field portions are offset, and an inductive voltage signal for the magnetic field portion from the conductor is output as a current detection signal. Then, the alternating current value of the conductor is calculated based on the current detection signal.